1. Field of the Invention
Generally, this application relates to position and orientation determination devices for surgery and other contexts. Specifically, this application relates to computer vision and ranging tracking systems for medical instruments and sensor probes.
2. Background
Currently, hand-held sensor systems are being used for several applications, ranging from environmental surveys of chemical, biological and radioactive environments, to medical investigations for diagnostics, disease characterization and intraoperative guiding and imaging. Because they are hand-held, they can be immediately positioned and oriented with almost all of the outstanding flexibility and adaptability of a human operator's hands.
In some instances, a user may wish to know exactly how and where a sensor system is pointed. Yet, the flexibility and adaptability of hand-held sensors also can make them difficult to track. Prior art approaches at spatial registration of sensors and instruments are bulky, cumbersome, expensive, or not practical. There are several examples in which sensor systems were outfitted with a Global Positioning System (GPS) antenna, Inertial Navigation Unit (INU), magnetic sensors, or optical markers.
Unfortunately, GPS only provides coarse, limited spatial resolution and does not work reliably when satellite GPS signals are weak. INU systems drift over time. Magnetic sensors are generally useful for tracking objects within a small volume of space, around 0.1 to 1 square meters (m3). In a controlled laboratory environment, magnetic sensors can provide location resolution of about 1 millimeter (mm) inside volumes around 0.2 m3 and orientation precision to within a degree. However, when used in realistic applications where metallic objects are present, or when other magnetic fields are generated by adjacent electronic equipment, the position resolution decreases to several centimeters within a 0.2 m3 volume. This position resolution is too coarse for many applications, including medical diagnostic and medical interventions where multiple electronic instruments and metallic objects are used. Optical markers attached to probes require a direct and continuous line of sight to an external Coordinate Measuring Machine (CMM) camera system. Generally, CMM camera systems are bulky, expensive and impractical for most applications in where hand-held systems are used or desirable.
U.S. Patent Application No. 2009/0259123 A1 proposes a CMM-type system for tracking hand-held sensors and instruments for intraoperative navigated sentinel lymph node dissection. The system proposed therein uses external infra-red cameras to track coded infrared reflective markers attached to the hand-held probes or hand-held instruments. One drawback of this approach is that a continuous line of sight needs to exist between external cameras placed above a surgery table and all of the markers placed on probes, instruments, and samples. The hands, arms, and heads of the surgeons may easily break the line of sight during surgery procedures.
U.S. Patent Application No. 2012/0253200 A1 uses an augmentation device in the form of a bracketed structure to be appended to an existing imaging probe to project a pattern of structured light onto the skin or an organ of a patient to facilitate stereo object recognition.
There is a need for better, less expensive, and more accurate and precise tracking of hand held sensors and medical instruments.